In today's vehicles various supplementary brakes are used to reinforce or supplement braking action. One example of a supplementary brake is a so-called retarder associated with the vehicle's transmission. Another example is an exhaust brake arranged to increase the engine's exhaust backpressure and thereby increase the load upon the engine.
Said retarder may be controlled by means of a retarder control lever situated in a driving cab of the vehicle, enabling a driver to set a desired braking action in a number of discrete steps. In one version a driver may choose between five different steps for effecting a certain braking action. In the first four steps different amounts of braking action are applied by means of the retarder. In the fifth step the retarder's maximum possible braking action is applied in conjunction with appropriate braking action of the exhaust brake. Drivers may experience problems because of braking action differing greatly between the fourth (highest but one) step and the fifth (highest) step, since it is so markedly different between them. This is particularly so at relatively low vehicle speeds at which the retarder cannot achieve a particularly large braking torque.
There is a need to improve braking of vehicles whereby supplementary brakes are used to reinforce or supplement the wheel brakes.
There is a need to provide a method for control of braking by means of at least one supplementary brake of a motor vehicle whereby the above disadvantages are reduced.